1. Field of the Invention
This invention relates to apparatus and methods for handling objects and, more particularly, to apparatus and methods for handling objects, such as articles of produce, for the purpose of sorting those objects according to visually ascertainable criteria, such as size, color, and defectiveness.
2. Background Art
Prior to transporting harvested produce to market, one of the major tasks which must be performed is that of properly sorting the produce. Typically, produce is sorted and packaged using a number of criteria, including size, shape, color, and quality.
The presorting of produce has a number of advantages for both consumers and produce growers. For example, through presorting, poor or spoiled produce can be removed prior to packaging, thereby reducing the likelihood of spoilage of the remaining produce during subsequent transportation and storage. The presorting of produce also permits consumers to purchase produce having general characteristics which are compatible with their needs. A restaurant owner, for example, may desire to consistently purchase some types of produce such that all of the pieces of such produce are of a substantially uniform size and quality. Further, the presorting of produce facilitates packaging and storing, since the sorted produce may usually be neatly arranged on trays or in crates.
In the past, the sorting of produce has been accomplished in a number of ways. Originally, produce was sorted entirely by hand, with the sorters being given instructions and training relating to the predetermined sorting criteria. Such a sorting method is quite imperfect and gives rise to numerous errors due to both human inconsistency and to varying applications of the sorting criteria by different individuals. Accordingly, although some hand sorting is still carried out in the produce industry, most produce sorting is now done mechanically.
One of the earliest types of mechanical sorters comprises an apparatus which conveys the produce over a series of holes or openings of progressively increasing size. For example, the produce may be directed over a series of rollers which are positioned progressively farther and farther apart. The smaller pieces of produce fall through the earlier rollers of the series, while the larger pieces are maintained on the rollers until the separation between successive rollers becomes large enough to admit them. By positioning separate collection devices or bins at various points beneath the rollers, the produce can thus be sorted according to size.
This somewhat crude apparatus for sorting produce by size has several significant drawbacks. Pieces of produce that are slightly too large to be received in a particular opening will on occasion nevertheless become jammed in that opening. Produce is damaged or bruised in this manner, as well as due to the fall necessitated. Pieces of produce also bounce across openings which are actually large enough to receive them, thereby falling through subsequent, larger openings and being sorted improperly.
Due to the above-mentioned drawbacks, attempts have been made to develop more efficient and reliable methods for sorting produce mechanically. One of the most promising sorting methods currently in use involves scanning the produce optically in order to ascertain its characteristics. This sorting method offers the potential for greatly increasing the accuracy and reliability of sorting by size, as well as the opportunity to sort on the basis of other visual characteristics.
Although the structural requirements for a suitable optical sorting apparatus vary somewhat depending upon the type of objects to be sorted, an effective optical sorting apparatus must generally perform three separate operations. First, the objects must be singulated. That is, the individual objects must be separated physically one from another. Secondly, each object must then be individually scanned or examined in order to ascertain its characteristics. Finally, the individual objects must be sorted mechanically based upon the information obtained during scanning. Thus, an effective sorting apparatus must make provisions for effective singulating, scanning, and mechanical sorting.
These three individual functions may be performed, either by a single machine, or by a number of separate cooperating devices. Some optical sorting systems are quite complex, while others remain relatively simple.
Singulation of produce may be accomplished using a number of techniques. In one type of singulating mechanism, produce is spread in a single layer upon a relatively slow moving surface and then accelerated onto a second conveying means. The acceleration causes adjacent articles of produce to become separated slightly from one another. One device using this singulating principle employs a rotating right circular cone. The produce is advanced up the conical surface toward the apex of the cone and then allowed to recede toward the outer edges of the cone before being deposited onto a second conveyor. As articles of produce move away from the apex of the cone, their speed increases, thereby slightly separating adjacent pieces.
A second type of singulating mechanism comprises a conveyor which is formed of a plurality of cup-like carriers. As pieces of the produce are dropped onto this conveyor, each piece of produce is received in a separate carrier cup.
Once the produce has been singulated, each piece must then be optically scanned individually to ascertain its characteristics. Scanning may also be accomplished by several methods. One such method utilizes one or more photocells and corresponding light sources which are directed across the path of the produce at the photocells. For example, a photocell and a corresponding light source may be positioned so as to detect the passing of all produce of a particular height. By using a sequence of such photocells, the height of each individual article of produce can be determined. A second photocell and light source may be positioned adjacent the first to measure the length of each article of produce. This can be accomplished by connecting the second photocell to an appropriate timing and summing circuit.
Alternatively, it is possible to use a single two-dimensional array of photocells and corresponding light sources. The size of each article of produce is then determined based on the magnitude of the total current emitted by the entire photocell array. Although both of these scanning methods have been somewhat successful in measuring size, it has not been possible to use them to determine other characteristics of the produce, such as color or quality.
The most promising optical scanning method currently in use employs a line-scan camera. Such a camera can readily function to measure the size of an article of produce quite accurately, and some are capable of measuring the sizes of several articles of produce simultaneously. Perhaps more importantly, however, line-scan cameras can be programmed to simultaneously determine the color of each article of produce, as well as to detect certain kinds of produce defects.
Once the characteristics used to distinguish articles of produce have been ascertained by scanning, the produce must be sorted mechanically in accordance with that predetermined sorting criteria. Sorting mechanisms for use with optical scanners are of two general types. The first employs a plurality of solenoid-activated rams which selectively knock individual articles of produce off the produce conveyor. The produce is thus grouped in an appropriate one of a series of storage containers in accordance with the sorting criteria.
A second type of sorting mechanism comprises a plurality of cup-shaped carriers which each hold a single article of produce. The bottoms of individual carriers may be selectively opened by actuation of any one of a plurality of solenoids, each located adjacent a different storage container. The appropriate solenoid to be activated is determined based on the scanning data, thereby allowing each article of produce to drop through the cup-shaped carrier into one of the storage containers for grouping according to the preselected sorting criteria.
In use, one of the above-described sorting mechanisms is connected to an optical scanning mechanism in some suitable manner. For example, a solenoid-controlled ram may be positioned immediately adjacent a photocell to form a scanning and sorting station. If the photocell detects a article of produce of the appropriate size, the adjacent solenoid is actuated so as to knock that article of produce off the conveyor into an adjacent storage area. Otherwise, the article of produce is conveyed to the next scanning and sorting station for visual evaluation according to an adjusted size criteria.
Alternatively, scanning may be performed by a camera which is connected to a computer. The computer temporarily stores scanning information relating to the size, color, and/or quality of each article of produce. Being further provided with information relating to the speed of the produce conveyor, the computer is then able to trigger the appropriate sorting mechanism when each article of produce reaches the location at which it should be removed.
The mechanisms for singulating, scanning, and sorting produce may be combined in a number of ways so as to effectively perform the entire sorting operation. For example, one type of machine which performs each of the essential operations comprises a conveyor having a plurality of carrier cups, the bottoms of which are capable of being opened selectively by solenoids along the line of travel of the conveyor. One article of produce is dropped into each carrier cup and scanned by a line-scan camera. Each article of produce is then deposited into an appropriate one of a series of sorting containers by selectively actuating the solenoid located adjacent to the appropriate sorting container. This is perhaps the most common type of mechanical produce sorter currently in use.
Devices employing carrier cups do not effectively singulate the produce. It is very common, for example, for two or more articles of produce to be deposited into a single carrier cup or to be otherwise stacked on top of one another when being optically scanned. Although efforts have been made to create mechanisms that detect when produce stacking has occurred, there has been little success in doing so. Consequently, stacked articles of produce are often perceived by the scanning device of a sorter as a single article of produce and accordingly sorted improperly. This impairs the proper sizing of produce, and also makes it difficult to obtain an accurate count of the number of articles of produce that have been processed.
Other complications result because in order to accurately determine all of the desired characteristics of the produce, it is necessary to scan each article of produce from two or more directions. In sorting devices employing carrier cups, a defective article of produce may drop into a carrier cup oriented in such a manner that the defect is entirely on the bottom side thereof. As a result, a single scanning device located above the carrier cup cannot detect the defect as the article of produce is scanned.
A further problem is that such sorters are slow and inefficient in their use of space. For example, in known sorter devices using carrier cups individual articles of produce are typically positioned 10 to 12 inches apart on the produce conveyor. This results in a great deal of unused space between each article of produce, increasing needlessly the size of the sorter. As the maximum speed of the conveyor is limited by the resolution of the scanning device, a substantial amount of time is also wasted due to the distance between adjacent articles of produce being handled by the sorter.
Another type of sorting device that is known includes a sorting section which tilts the objects to the side of the conveyor after they have been scanned. Objects to be sorted by the device are conveyed to a scanning station. The optical scanning device detects preselected information about the objects which is stored in a data processing memory and thereafter used to operate the sorter section of the apparatus to selectively unload the objects by tilting them off the conveyor at different locations so as to group the objects according to preselected sorting criteria. Examples of this type of device are illustrated in U.S. patent applications Ser. Nos. 515,313 and 516,450.
A brief understanding of the structure and functioning of the sorter section of such a device will be facilitated by reference to FIGS. 17-19., The sorter section of this type of device can be seen to comprise a continuous chain A and a plurality of distinct types of sorter pieces that are releasably attached thereto. The sorter pieces include a mounting element B that is releasably connectable directly to the top of chain A by resilient legs C. As clearly shown in FIG. 18., the top of mounting element B is formed into a flat elongated support face D that is used to uphold objects to be sorted. Pivot pins E extend outwardly parallel to chain A from each side of mounting element B.
Each pivot pin E receives a rocker element F, the second type of sorter piece. The top of rocker element F accordingly rests adjacent to and is generally coplanar with support face D of the mounting element B by which it is upheld. Once mounted, rocker element F is capable of upward pivoting about pivot pin E.
Mounting element B and the two rocker elements F pivotably upheld on either side thereof together form a link set I. Releasably securable directly to the top of chain A at the outside of each link set I, is the third type of sorter piece, a spacer element J. The top of each spacer element J is provided with an elongated flat support face K which is similar in shape, orientation, and function to support face D on the top of each mounting element B. When attached to chain A adjacent to rocker element F, spacer element J serves to hold rocker element F on pivot pin E of mounting element B as chain A makes its return. Chain A is filled along its entire length by link sets I and intervening spacer elements J attached in this manner.
The space between the raised ribs G of consecutive pairs of rocker elements F defines a carrying pocket L which receives individual objects from the scanning station of the apparatus. FIG. B illustrates that carrying pockets L are formed both within and between successive link sets I on chain A.
Simultaneous pivoting of the two consecutive rocker elements F at the sides of a carrying pocket L will cause rocker element support faces H to encounter the object in the carrying pocket. Further pivoting of the rocker elements will then lift and tilt the object off the conveyor, tipping the object off the side of the sorting section. In this manner individual objects can be selectively removed at any of a number of different sorting locations along the sorter section.
The process of pivoting consecutive pairs of rocker elements F to tilt an object out of conveying pocket L therebetween does not require striking the object. The motion involved is smooth and gradual and does not cause damage to the objects. Nevertheless, even the improved sorter section components depicted in FIG. 17 are afflicted with significant disadvantages.
For example, emptying a single conveying pocket L requires the upward tilting of both rocker elements F on either side thereof. This is accomplished through the use of projecting feet M extending from each rocker element E and a plurality of stationary ramps N located along chain A near the line of travel of projecting feet M. Movement of chain A in the direction indicated by arrows P draws projecting feet M toward and past each ramp N. Normally, projecting feet M do not interact with ramps N. In this case no unloading of objects occurs.
On the other hand, if unloading of a specific object at a given discharge point is appropriate, a selectively operable diverter arm Q at the lead end R of ramp N is mechanically or electrically brought into an activated position. In that position projecting feet M of the two rocker elements F on either side of the object are diverted out of their normal line of travel, onto and over ramp N. In the process, the rocker elements F to which projecting feet M are attached are tilted upwardly, lifting and tipping the object in carrying pocket L from chain A.
Two functional flaws have become apparent in this manner of operation. As shown in FIG. 19, for a chain A moving in the direction indicated by arrow P, the upward motion imparted to any pair of rocker elements F is not strictly simultaneous. In relation to carrying pocket L.sub.3 projecting leg M.sub.1 of lead rocker element F.sub.1 encounters diverter arm Q before projecting leg M.sub.2 of trailing rocker element F.sub.2. Correspondingly, the lead side of any object in carrying pocket L.sub.3, will be lifted in advance of the trailing side of that same object. Rather than directing the object from chain A in a direction normal thereto, this has the effect of initially tilting the contents of the carrying pocket L.sub.3 backwards in relation to the motion of chain A. Objects discharged from the sorting section of the device of FIG. 19 are thus tipped from chain A in an imprecise manner, using a somewhat complex motion.
Furthermore, the mechanics of raising both rocker elements together in order to discharge a single object is complicated. For each single object discharged, diverter arm Q must remain in its activated position long enough for two rocker elements to be drawn past. This mechanical functioning is a challenge to coordinate, requiring highly precise operation of the machinery involved and, where an attempt is made to automate the sorter to its optimum degree, complex software.
Another disadvantage results. Rocker element F has on the top thereof two rocker element support faces H, one on either side of raised rib G. Each of these two rocker element support faces H form a part of two different adjacent conveying pockets L. Thus, rocker element support face H.sub.1 on rocker element F.sub.1 is part of carrying pocket L.sub.3, while rocker element support face H.sub.2, also on rocker element F.sub.1, is part of carrying pocket L.sub.1. This fact has negative implications. The practical consequence is that objects in conveying pockets on both sides of the one from which an object is to be discharged must endure jostling, even when not being removed from the sorter section. An ideal sorter would permit each object to be unloaded individually, without imparting movement of any kind to objects being carried in adjacent conveying pockets.
In order to avoid this result, objects are frequently carried only in alternate, rather than in successive, conveying pockets L. As a result, however, half of the length of chain A of the sorter section of such devices is empty. The object handling rate of the device is thus effectively halved, and complicated feed mechanisms must be devised for supplying objects from the scanning station to the sorting section so that only alternate conveying pockets L are filled.